Brain tumors are among the leading causes of cancer-related deaths in the United States, with glioblastoma multiforme (GBM) being one of the most aggressive and difficult subtypes to treat. In this proposal we plan to pursue a strategy to treat malignant glioma with the potent antitumor cytokine, interferon-beta (IFN2). Type I (1/2) interferons (IFNs) have long been recognized for their significant, pleiotropic anticancer activity. However, despite significant activity in preclinical models against a variety of tumor types, including gliomas, the antitumor efficacy of IFNs in clinical trials has been disappointing. A significant contributing factor includes the development of resistance to IFN-mediated cell death through downregulation of apoptotic pathways. We have established that nuclear factor kB (NFkB) promotes cell survival and suppresses the expression of a subset of IFN target genes that are likely effectors of IFN's antitumor activity. Unfortunately, not only is NFkB constitutively active in many cancers, including glioma, but it can also be activated by IFN itself. This finding suggests that the potent anticancer activity of IFN may be counterbalanced by NFkB activity. Based on these observations, we hypothesize that selective inhibition of NFkB will enhance the anticancer activity of IFN. We will perform a systematic and detailed evaluation of the role of NFkB in regulating the anticancer action of IFN2 in glioma cells. Based on the insights gained, we will select and test complementary agents that should provide synergistic antitumor activity with IFN. After confirming the synergy of these agents in vitro, we will test the effectiveness of combination therapy that includes IFN in relevant preclinical models of malignant glioma. The overriding goal of this project is to increase the antitumor activity of IFN through an improved understanding of IFN2's mechanism of action against glioma and the factors that work against it. In specific aim 1 we will examine the role of NFkB in suppressing the anticancer activity of IFN2 in gliomas. To test this, we will determine in glioma cell lines 1) the contribution of the classical NF:B pathway to constitutive and IFN-induced NF:B activity; 2) the contribution of the alternative NF:B pathway to constitutive and IFN-induced NF:B activity; and 3) the effects of pharmacological and genetic NF:B inhibitors on IFN activity. Based on these findings, we will test the effects of clinically available NFkB inhibitors on IFN's anticancer activity in relevant, preclinical rodent models of malignant glioma. In specific aim 2 we will characterize the role of NFkB in regulating IFN target genes and the role of these target genes in the anticancer action of IFN2 in gliomas. To test this, we will: 1) characterize the induction of these genes in response to IFN; 2) determine their importance in effecting the anticancer activity of IFN in vitro and in vivo and 3) translate these findings by testing the efficacy of appropriately selected combination therapy in relevant, preclinical models of malignant glioma.